1. Field of the Invention
The present invention relates generally to improved rod guide apparatus, and more particularly, but not by way of limitation, to an improved rod guide apparatus formed of plastic material for reciprocating rods such as sucker rods in oil wells.
2. Description of the Prior Art
A variety of rod guides, paraffin scrapers and the like have been developed and used for protecting rods which are reciprocated within a conduit. For example, sucker rods in pumping oil wells normally extend longitudinally through tubing diposed in the well bore and are reciprocated therein during pumping of the well. In order to prevent the sucker rods from engaging the walls of the tubing during the reciprocation thereof and the consequent wear on the rods, rod guides attached to the rods at intervals have been utilized. In oil wells which produce heavy hydrocarbons such as paraffin which deposit on the sides of the tubing, scrapers which also functions as rod guides have been used.
A particularly suitable rod guide and paraffin scraper is described in U.S. Pat. No. 3,399,730 dated Sept. 3, 1968. Such rod guide or paraffin scraper is formed of a plastic material which insulates a metal rod from electrolytic action and the consequent corrosion damage. The rod guide or paraffin scraper is comprised of two substantially identical half sections which include semicircular recesses therein and which are adapted to be lockingly clamped together against opposite sides of the outer periphery of the rod whereby the rod extends through a circular bore formed by the semicircular recesses in the half sections. In use of the rod guides or paraffin scrapers, they are attached to the rod at intervals along the length thereof thereby preventing the rod from contacting the tubing or conduit within which it is reciprocated.
While the rod guide or paraffin scraper described in U.S. Pat. No. 3,399,730 includes a plurality of longitudinal rib members positioned on the surfaces of the semicircular recesses in the half sections which bite into or cut through any corrosion or coating which is present on the outer periphery of the rod when the apparatus is installed thereon, problems have been encountered as a result of the guide apparatus slipping longitudinally on the rod. Such slippage is primarily due to the fact that the outside diameter of sucker rod and the like is not uniform, and if the outer periphery of the rod is of a smaller diameter or a diameter equal to the inner periphery of the bore in the guide apparatus at the outer edges of the ridges therein, a tight fit between the outer periphery of the rod and the guide apparatus is not achieved. In addition, even where a tight fit between the apparatus and the rod is achieved upon installation of the apparatus, the force exerted on the guide apparatus as the rod is reciprocated due to the guide apparatus scraping the walls of a conduit within which it is disposed causes the guide apparatus to be enlarged whereby the rod can contact the tubing and cause damage thereto.
By the present invention an improved rod guide and/or paraffin scraper apparatus is provided which, when clamped on a rod, resists lateral slippage even when high lateral forces are exerted on the apparatus. Further, the improved rod guide apparatus of the present invention can be clamped on rods having variations in outside diameter and still resist longitudinal slippage.